Human rights activists in Iran have reported that at least six detainees have died in prisons over the past two months.

In a rare public statement, President Hassan Rouhani has announced the appointment of a four-member committee to investigate what it called “detention houses “in the country.

“President Rouhani appointed a four-member committee to investigate and deal with regrettable incidents in a number of detention houses. The committee is tasked with investigate[ing] the issues and report back to the President about the possible negligence in this regard,” the presidency website said on Wednesday.

The committee comprises some of the highest members of Iran's government, the ministers of interior, intelligence, and justice, as well as vice president for legal affairs.

Human rights activists reported that at least six detainees have died in prisons over the past two months in Iran. The judiciary has confirmed three deaths in custody but said all three had committed suicide.

Kavous Seyed-Emami, an Iranian-Canadian sociology professor, was arrested on January 24 and died in prison. Iran’s judiciary said Seyed-Emami, 63, had committed suicide.

Seyed-Emami was the managing director of the Persian Wildlife Heritage Foundation.

Tehran’s prosecutor, Abbas Jafari-Dolatabadi, was quoted as saying by state media this week that Seyed-Emami had set up the NGO as a cover to collect classified information on Iran’s missile programme.

“They had installed cameras in strategic locations in Iran under cover of monitoring the environment, but in reality, they were monitoring Iran’s missile activities,” Dolatabadi said.

He said on Wednesday that Seyed-Emami’s “suicide” was a blow to their investigations.

Nine other staff members of his organisation have also been arrested, according to the Center for Human Rights in Iran (CHRI), a non-profit group based in New York.

Seyed-Emami's family called for an independent investigation into his death and said they were under pressure from authorities not to publicise the case.

His son Raam Emami said his mother was summoned by judicial officials last week “to meet with her husband” but was then informed of his death, according to Reuters news agency.

Raam said in a statement on Wednesday: “We have a right to know why my father was arrested and the circumstances that led to his passing ... We will use every legal channel at our disposal toward an independent investigation.”

The Canadian government said on Tuesday it was “seriously concerned” about the circumstances surrounding Seyed-Emami's death and has pressed Iran for details.